An isobar model for η photo- and electroproduction on the nucleon

Eta photo- and electroproduction on the nucleon is studied using an isobar model. The model contains Born terms, and contributions from vector-meson exchanges and nucleon resonances. Our results are compared with recent eta-photoproduction data for differential and total cross sections, beam asymmetry, and target asymmetry, as well as electroproduction data. Besides the dominant S-11(1535) resonance, we show that the second S-11 resonance, S-11(1650), is also necessary to be included in order to extract S-11(1535) resonance parameters properly. In addition, the beam asymmetry data allow us to extract very small (< 0.1%) N* --> etaN decay branching ratios of the D-13(1520) and F-15(1680) resonances because of the overwhelming s-wave dominance. This model (ETA-MAID) is implemented as a part of the MAID program (the MAID program can be accessed from the webpage: http://www.kph.uni-mainz.de/MAID/maid.html). (C) 2002 Elsevier Science B.V. All rights reserved.